Late last night, VMware announced it had acquired Desktone, a company that provides virtual desktops as a service, which (among other things) allows users on mobile platforms to access Windows apps from non-Windows devices.

At first glance, this is a little puzzling given that VMware already has its own technology for doing the same thing. Here's what VMware is doing.

Both VMware and Desktone play in the virtual desktop infrastructure (VDI) space. The idea is that instead of offering Windows apps in the traditional way -- running locally on a user's PC -- a company will create a number of virtual Windows desktop configurations on a server, then offer them over the network to users as needed. This was originally positioned as a cost benefit: Instead of updating Windows images and apps on a bunch of individual PCs, VDI would let companies take care of updates in a central place. Users would simply see the updated desktop the next time they logged on. In theory, companies could also save on hardware by buying thin client terminals instead of PCs for each user, although they'd still have to pay Microsoft for a Windows license for each user.

Over the last couple years, as mobile devices running iOS and Android have started to invade the enterprise, some customers have started to look to VDI as a quick and dirty way to provide longstanding enterprise apps to non-Windows devices. It's not an ideal solution -- performance can be laggy over a network, and the non-touch interface of traditional Windows apps seldom lend themselves to a touch device like an iPad or Android phone -- but it's quicker and generally cheaper than rebuilding or refactoring enterprise apps for mobile platforms.

The confusing thing about this purchase is that VMware already has a VDI solution called View, which competes primarily against Citrix Receiver. Earlier this year, View was subsumed into the VMware Horizon family of products, which includes tools for managing mobile devices and apps. At that time, View also added VMware's Unity Touch interface, which was meant to make traditional Windows apps work better on touch devices.

So why did VMware buy another VDI provider?

Because Desktone does not provide VDI technology directly to customers. Rather, it provides a platform for service providers such as Dell, Fujitsu, and NEC, to host their own VDI solutions, which they resell to customers. Desktone is a pioneer in this area, as it figured out how to create a multitenant VDI solution -- necessary for service providers to deliver desktops on a massive scale -- without violating Microsoft's licensing terms. In fact, Desktone actually trademarked the terms "Desktop as a Service" and "DaaS" (not to be confused with "data as a service") back in 2009.

This DaaS model allows smaller companies to gain some of VDI's benefits, such as running Windows apps on mobile devices, with the security and control that IT has come to expect, without having to invest in the complicated infrastructure (and license tracking) needed to do it in house.

By buying Desktone, VMware can propagate the idea of desktop virtualization to customers it might not reach otherwise. Also, VMware already has customers who want a combination of their own VDI technology and a hosted DaaS solutions -- for example, a hosted solution might work better for branch offices.

Desktone also has some other interesting technology, such as the ability to manage virtual desktops in multiple geographies using a single management pane, as Gartner analyst Gunnar Berger explained in a blog post on the deal.

For the time being, VMware will continue to sell Desktone to service providers -- and will use its own channel to push Desktone -- but it's conceivable that VMware could offer DaaS directly to customers at some point.

For more information on the deal, read Sanjay Poonen's blog post on it. Poonen was the President of Innovation and Technology for SAP, but left to run VMware's End-User Computing Group earlier this year.